Scientists Help Galapagos Finches Get Rid Of A Nasty Nest Pest

A Darwin finch in the Galapagos. The subfamily that is unique to the islands has been threatened by an invasive parasite that first appeared in 1997.

Education Images
/ UIG via Getty Images

Originally published on May 6, 2014 6:52 pm

The diminutive Galapagos finches had a problem: The larvae of a parasitic nest fly were killing off their hatchlings.

A scientist, with the help of crowdfunding, had a solution: offer the birds insecticide-laced nest-building material.

It worked.

According to a study published in Current Biology, the birds — really 15 different species known as Darwin's finches — were offered cotton soaked in a chemical formulated to kill the fly Philornis downsi. The finches eagerly snatched up the cotton balls and wove them into their nests.

The parasitic fly first appeared in Ecuador's Galapagos Islands in 1997, arriving most likely aboard planes and ships. Since the pest isn't native to the islands, "Darwin's finches have not had enough time to evolve defenses against the parasites," Dale Clayton, the study's co-author and a University of Utah biology professor, told Reuters.

"In some years, 100 percent of nestlings die as a direct result of the parasites," he said. "It is critical to find a way to control the parasites in order to help the birds."

Scientific American says the inspiration for using treated cotton for the self-fumigation came to study co-author Sarah Knutie in 2010. Knutie was sitting on the porch at the Charles Darwin Research Station on Santa Cruz Island in the Galapagos ruminating over the Philornis problem when she "noticed finches taking a laundry line back to their nests."

When Knutie, a conservation ecologist at the University of Utah in Salt Lake City, provided a stash of cotton balls, the birds took those, too.

Scientific American writes:

"A few years later, during a workshop on pest-control ideas, she proposed putting insecticide-soaked cotton balls in dispensers for the birds to take back to their nests.

" 'I don't know that I was taken seriously, but I thought it could be an immediate solution,' she says."

But Knutie wanted to give it a try. She used crowdfunding site RocketHub to raise money for plane fare and supplies.

According to Scientific American:

"Between January and April, during the finch breeding season, the team distributed 30 cotton dispensers throughout a study site measuring roughly 600 by 80 meters. Half of the dispensers contained cotton treated with dilute permethrin, an insecticide commonly found in head lice shampoo; the rest contained cotton treated with water.

"By the end of the breeding season, the authors had located 26 nests, 22 of which contained cotton. The nests woven with insecticide-treated cotton harbored about half as many flies on average as the nests woven with water-treated cotton. Further inspection revealed that insecticide effectiveness depended on the dose: seven of the eight nests that contained at least one gram of insecticide-treated cotton had no parasites at all."